Thursday, January 15, 2009

Ethological Miscellany

- This past year, more reports of young bull elephants attacking rhinoceroses and turning on members of their own clans appeared in international papers and journals. Biologists believe that this rise in unprovoked violence is the result of prematurely elevated testosterone levels in the elephants. Because older bulls are not present in many elephant herds, the social hierarchy necessitates that younger males fill the role many years before they would normally be expected to do so. As they assume the mantle of seniority, they experience chemical changes, including a marked increase in the production of testosterone. The absence of older bulls is attributed to federal culling programs. These well-intentioned programs were instituted to reduce the stress of overcrowding within African elephant (Loxondonta africana) populations, but because the professional hunters usually kill the larger, older animals, they have unintentionally upset the social dynamic.

- In May 2008, biologists reported that wild three-toed sloths sleep 9 1/2 hours a day, whereas their captive counterparts sleep an average of 16 hours a day.

- I recently learned of a Jamaican man who, highly regarded as an artist in his home country, decided to move to the United States in the 1970s. He settled in Baltimore, Maryland, where he would live for many years. Yet, for some unknown reason, the man was no longer compelled to make art. Although he continues to reside in Baltimore, he only paints when he returns to Jamaica to visit family and friends.

- Biologists report that epaulette sharks (Hemiscyllium ocellatum) living in and around Australia's Great Barrier Reef shut down most of their nervous system and go blind when their environment becomes starved of oxygen. Because the sharks live on shallow parts of the reef, at low tide they can become isolated in large tidal pools, temporarily cut off from the ocean. These tidal pools commonly are hypoxic (having very low oxygen levels). To prevent suffocation, the sharks' electrical activity ceases. Because electricity consumes fifty percent of nervous system energy consumption, shutting down the nervous system allows the animal to survive.